1. Field of the Invention
The present invention relates to a beam scanning apparatus for projecting light onto a photoreceptor in a device such as an electrophotographic printer.
2. Description of the Related Art
In general, a beam scanning apparatus adopted in a printer photosensitizes a photoreceptor through a main scan by a beam deflector and a sub scan by transfer or rotation of the photoreceptor.
Referring to FIG. 1 which shows the optical arrangement of a conventional beam scanning apparatus, the beam scanning apparatus includes an optical source 1, a beam deflector 4 for deflecting a beam of light emitted from the optical source 1, and an f-theta (f-.theta.) lens 7 for correcting an error of light deflected by the beam deflector 4.
A condensing lens 3 is installed between the optical source 1 and the beam deflector 4 to condense the beam of light emitted from the optical source 1. The beam deflected by the beam deflector 4 is reflected by a reflective mirror 8, and the reflected beam travels toward a photoreceptor (not shown) such as a photoreceptor belt.
The beam deflector 4 is comprised of a motor 5 and a rotating polygonal mirror 6 rotated by the motor 5. The beam emitted from the optical source 1 is deflected according to the angle between the beam and a reflective plane of the rotating polygonal mirror 6. Accordingly, the beam deflection is sensitive to wobbles generated upon rotation of the rotating polygonal mirror 6.
Also, a color printer must have a special beam scanning apparatus corresponding to a specific color, thereby rendering the device complicated and large.